1. Technical Field of the Invention
The present invention relates to an intake apparatus of an engine mounted on a motorcycle or the like.
2. Description of the Related Art
In the conventional motorcycle, a cowling 56 as shown in FIG. 9 is attached to a front side of a motorcycle body. The cowling 56 is provided, on a front side thereof, with an air-introducing duct 58 having air inlets 57 allowing air in a motorcycle engine (Japanese Patent Publication No. 2704369). At the rear end of the air-introducing, duct 58, an intake duct 60 is connected to the duct 58 through the intermediary of a rubber seal 59, as shown in FIG. 10. In FIG. 9, the air inlets 57 are arranged on both sides of the underside of a head lamp unit 61. In the modification, they may be arranged on both sides of the head lamp unit 61 or both sides of the upside of the unit 61.
In the above-mentioned constitution, however, since the air-introducing duct 58 is formed integrally with the cowling 56, the air inlet 57 is influenced in terms of its opening area and profile by the profile and dimension of the cowling 56. Therefore, there is a case that the degree of freedom in design of the port 57 is not only reduced but also causing the difficulty of taking air in a position where the running wind pressure is sufficiently great. Alternatively, when the opening area and profile of the air inlet 57 have to be altered for increasing engine output etc., the above-mentioned constitution needs to change the entire cowling 56 to another one.
Under such a situation, it is therefore an object of the present invention to provide an intake apparatus for a vehicle engine, which is capable of taking the air under a higher running wind pressure and which allows to select the opening area and profile of the air inlet.
According to the present invention, as the first feature, there is provided an intake apparatus of an engine for a vehicle having a cowling fitted to a front of a vehicle body, the intake apparatus comprising:
an intake duct for introducing air into the engine; and
an air-introducing duct connected to the upstream end of the intake duct to form an air inlet of the engine;
wherein the air-introducing duct is constituted independently of the cowling and arranged so that a leading end of the air-introducing duct occupies ahead of a leading end of the cowling.
In the so-constructed intake apparatus, the leading end of the air-introducing duct is arranged ahead of the leading end of the cowling. Therefore, there can be obtained a high running wind pressure at the leading end of the air-introducing duct, in comparison with the running wind pressure at the leading end of the cowling. Consequently, it is possible to improve an output of the engine. Further, since the air-introducing duct is constituted independently of the cowling, it is possible to further improve the engine output upon the option of the air inlet in terms of its opening area, profile, etc.
Further to the intake apparatus of the first feature, the second feature of the invention resides in that the air-introducing duct is adapted so that an air passage formed therein extends along its longitudinal axis making a designated angle to a horizontal plane, i.e. a level. The designated angle is established so as to realize the vehicle""s optimum condition at a vehicle""s design speed. Note, the vehicle""s design speed designates a predetermined speed allowing of enhancing a variety of vehicle""s characteristics, for example, its controllability, engine output, fuel consumption, etc. The vehicle""s optimum condition nominates a condition under which the running wind pressure of fresh air introduced through the air inlet can be maximized at the vehicle""s design speed.
In this way, since the running wind pressure can be maximized at the vehicle""s design speed, it is possible to improve the engine output.
Further to the intake apparatus of the first feature, the third feature of the invention resides in that the air-introducing duct is formed so that the leading end has a bell-mouth configuration. It is noted that the bell-mouth configuration designates a profile that the air passage is gently enlarged toward its upstream end in order to reduce a pressure loss of the fresh air.
According to the third feature of the invention, since the air being introduced through the so-constructed air inlet has a reduced pressure loss owing to the bell-mouth configuration, it is possible to improve the engine output as much.
Further to the intake apparatus of the second feature, the fourth feature of the invention resides in that the designated angle is substantially 0 degree under condition that the vehicle travels at a vehicle""s design speed.
According to the fourth feature of the invention, when the vehicle is travelling at a vehicle""s design speed, the air passage formed in the air-introducing duct extends substantially parallel to the horizontal plane, i.e. the level. In this way, the maximum running wind pressure can be obtained.
Further to the intake apparatus of the fourth feature, the fifth feature of the invention resides in that the designated angle ranges from about 3 to about 6 degrees while the vehicle with no rider stops.
According to the fifth feature of the invention, owing to the above establishment of the angle of the air, it is possible to attain the angle of the air passage of substantial zero (0) degree under condition that the loaded vehicle travels at the vehicle""s design speed. In this way, the maximum running wind pressure can be obtained the angle of substantial.
According to the present invention, as the sixth feature, there is also provided an intake apparatus of an engine for a vehicle having a cowling fitted to a front of a vehicle body, the intake apparatus comprising:
an intake duct for introducing air into the engine; and
an air-introducing duct connected to the upstream end of the intake duct to form an air inlet of the engine;
wherein the air-introducing duct is constituted independently of the cowling and also fastened to the cowling by at least one fastening member inserted from the interior of the cowling.
In the intake apparatus in accordance with the sixth feature, the air-introducing duct is fastened from the interior side of the cowling. Thus, it is possible to reduce irregularities appearing on the inner face of the air-introducing duct, whereby the pressure loss of the intake air can be decreased thereby to obtain the running wind pressure as much. Additionally, since there is a great space defined in the cowling, the attaching or detaching operation of the air-introducing duct against the cowling can be performed with ease. Therefore, even when altering the air-introducing duct to another one, there is no need to change the cowling but the air-introducing duct. It is possible to select an opening area of the air inlet, the profile, etc. easily.
Further to the intake apparatus of the sixth feature, the seventh feature of the invention resides in that the air-introducing duct is arranged so that a leading end of the air-introducing duct occupies ahead of the leading end of the cowling.
Also in this case, the running wind pressure at the leading end of the air-introducing duct becomes larger than the running wind pressure at the leading end of the cowling. Consequently, it is possible to improve the engine output.
Further to the intake apparatus of the seventh feature, the eighth feature of the invention resides in that the air-introducing duct is provided, at a downstream side thereof, with an enlarged socket part into which the intake duct is inserted.
Owing to the provision of the enlarged socket part, it is possible to reduce a step produced an inner wall of the inserted intake duct and the inner face of the air-introducing duct, whereby the pressure loss of the fresh air flowing in the air-introducing duct can be reduced.
Further to the intake apparatus of the eighth feature, the ninth feature of the invention resides in that the intake apparatus further comprises a screen in the form of a mesh. The mesh type of screen is disposed in the air-introducing duct and also interposed between an upstream end of the enlarged socket part and the intake duct.
In this case, there is no need to prepare any means of positioning the screen in the air-introducing duct.
The above and other features and advantages of this invention will become apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing a preferred embodiment of the invention.